Blister packaging is commonly used to store medication. This type of packaging typically comprises a number of blisters formed by a thermoformed plastic that is attached to a backing made of paperboard, metallic material, or plastic. One or more pills or tablets may be stored within each of the cavities formed by the blisters. When the patient wishes to take the medication, he or she simply ruptures the portion of the backing corresponding to the appropriate blister to release the stored medication.
One example of a blister packaging for medication contains 28 cavities, arranged in 4 columns and 7 rows of cavities. Each row may correspond to a day of the week, with each column corresponding to a particular time of day (e.g. morning, afternoon, evening, bedtime, etc.). This packaging allows the patient to store a medication regimen for an entire week using a single blister pack.
In order to ensure that medication is taken in accordance with a prescribed schedule, blister packs may be provided with electronic means (e.g. circuits) for detecting when the cavities are ruptured. However, if such electronic means are bulky or cumbersome, these “smart” blister packs may face difficulties in market adoption since pharmacies may have limited shelf space. Furthermore, the cost of producing the smart blister packs should not be so high such that pharmacies and patients are discouraged from using them.
For example, United States Patent Publication No. 2015/0148947 to McConville et al. discusses a device for determining when a medication is removed from a blister pack. Each blister of the blister pack has a corresponding circuit on the backing with a different resistance associated with each circuit. When a cavity is ruptured, the corresponding circuit is broken, resulting in a reduction in the overall resistance in the device, which is detected by a controller. Although McConville et al. discusses the possibility of printing circuits directly on the backing of the blister pack, limitations in the printing process typically results in a high degree of variability in the resistances in the resulting circuits. This makes the approach in McConville et al. impractical when a large number of blisters is required, as it is very difficult to ensure that the resistances in each of the circuits will be sufficiently differently from one another to be distinguishable when a circuit is broken.
U.S. Pat. No. 8,960,440 to Kronberg also discusses a device for monitoring when cavities on a blister pack are ruptured. The device comprises a number of breakable resistive traces (each applied to the backing of a cavity) connected in parallel to each other, which is connected in series with a reference resistive trace. When a cavity is ruptured, the corresponding resistive trace is broken, resulting in a microcontroller detecting a change in the ratio of the resistance of the (parallel) breakable resistive traces with respect to the reference resistive trace. Although the device in Kronberg is able to detect that a cavity has been ruptured, it is not able to detect which particular cavity has been ruptured.
There is therefore a need for a blister pack that is both cost-effective to produce and yet capable of detecting when particular cavities are ruptured.